1. Field of the Invention
This invention is in the field of paper winding assemblies and, more particularly, to a control system for raising and lowering a rider roll into variable pressure applying relationship with a roll of paper being wound up. The invention also includes an improved double diaphragm valve assembly which translates differences in air pressure into differences in hydraulic pressure used to raise and lower a rider roll.
2. Description of the Prior Art
It is well known that in winding large diameter rolls of paper wherein the roll of paper is placed on power driven winding drums and rotatably driven, as the web material is wound about its winder shaft the wound roll increases in hardness as the diameter and the weight of the roll increases, with the result that a nonuniform density may result in the rewound roll of paper. This density can be controlled by the use of a rider roll bearing on the top of the roll of paper and applying pressure on the roll by virtue of its own weight. Suitable lifting mechanism may be provided to opposite ends of the winder shaft to remove some of the weight of the roll of paper from the nips between the roll of paper and the winding drums.
In Daly, U.S. Pat. No. 3,282,526, there is described a drum winder for paper in which the nip pressures between the roll and the winding drums is relieved by applying a lifting force to the opposite ends of the winder shaft and by subjecting the winder shaft to an oppositely directed cantilever bending action. This action counteracts the deflection of the winder shaft so that it assumes an S-shaped deflection curve and more nearly approaches a straight line, and thereby tends to produce a more uniform density in the roll.
Dorfel, U.S. Pat. No. 3,604,649 refers to a different type of rider roll assembly for securing a uniform winding tightness along the width of the web and between adjacent layers of the wound roll. A rider roll is positioned in pressure engagement with the generated surface of the wound roll and diametrically opposite thereto, there is a loading roller which is operable to apply a variable force to the wound roll corresponding to the increasing weight of the wound roll so that the contact pressure between the wound roll and the rider roll is maintained constant or varies in a predetermined manner.
One of the problems associated with a rider roll assembly is that of vibration, particularly during high speed winding operations. In Dahl et al, U.S. Pat. No. 4,047,676, there is described a means for dampening this vibration, utilizing a device which has an elongated hollow tube fitting into or attached to one side of the beam which is coextensive with the rider roll. The rider roll is mounted at its ends and bearings on the beam. Within the outer stationary hollow tube or cylinder there is an inner beam and a continuous elastic tubing is annularly or spirally wound around this inner beam. Between the outside of the tubing on the inner surface of the tubular member there is a layer of steel slats which extend parallel to the axis of the beam. At the outer surface of the slats there is laminated a sheet of fibrous material. The tubing is inflated with a desired air pressure to force the slats outwardly against the inner surface of the cylindrical tube and thereby provide for energy absorption transferred from the beam to the cylinder.
Previously used systems for adjusting rider roll pressure sometimes made use of separately functioning air and oil valves for the pneumatic and hydraulic portions of the control circuit, respectively, in combination with a solenoid. This type of system is reasonably complicated and provided possible areas of failure in numerous places. Some rider roll balancing systems made use of relatively massive counterweights. Such expensive deadweighting is not practical for relatively large rider roll systems.